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10
examples/USER/qtb/README Normal file
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There are example scripts for using the USER-QTB package.
See its src/USER-QTB/README file for more info on
quantum nuclear effects and when they are important
to include in your model.
Authors Information and Contact
The person who created this package and these examples is Yuan Shen
(sy0302 at stanford.edu) at Stanford University. Contact him directly
if you have questions.

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#This script implements the BKS pair potential for various silicon dioxide compounds. Inner part is fixed with a harmonic potential. Long range Coulomb interactions are evaluated with the pppm method.
#Pair Potentials
pair_style hybrid/overlay buck/coul/long ${cut_off} table linear 39901
pair_coeff 1 1 buck/coul/long 0.0 1.0 0.0 #No interactions between Si atoms
pair_coeff 1 2 buck/coul/long 18003.757200 0.205205 133.538100
pair_coeff 2 2 buck/coul/long 1388.773000 0.362319 175.000000 #BKS interaction in PRL 64 1955 (1990)
pair_modify shift yes
pair_coeff 1 2 table potential_SiO2.TPF Si-O ${cut_off}
pair_coeff 2 2 table potential_SiO2.TPF O-O ${cut_off} #See the potential file for more information
kspace_style pppm 1.0e-4
#Neighbor style
neighbor 2.0 bin
neigh_modify check yes every 1 delay 0 page 100000 one 2000

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## This script first uses fix qtb to equilibrate alpha quartz structure to an initial state with quantum nuclear correction and then simulate shock induced phase transition through the quantum thermal bath multi-scale shock technique
variable x_rep equal 2 #plot is made with x_rep = 8 #x-direction replication number
variable y_rep equal 1 #plot is made with y_rep = 5 #y-direction replication number
variable z_rep equal 4 #plot is made with z_rep = 15 #z-direction replication number
variable cut_off equal 10.0 #Cut-off distance for the Buckingham term (Angstrom in metal units)
variable pressure equal 1.03125 #Initial state pressure (bar in metal units)
variable temperature equal 300.0 #Initial state quantum temperature (K in metal units)
variable delta_t equal 1.0e-3 #MD timestep length (ps in metal units)
variable damp_qtb equal 1 #1/gamma where gamma is the friction coefficient in quantum thermal bath (ps in metal units)
variable v_msst equal 78.0 #Shock velocity (Angstrom/ps in metal units)
variable q_msst equal 40.0 #Box mass-like parameter in the MSST (mass^2/length^4, where mass=grams/mole and length=Angstrom in metal units)
variable tscale_msst equal 0.05 #Temperature reduction parameter in the MSST (unitless)
variable eta_qbmsst equal 1.0 #Coupling constant between the shock and the quantum thermal bath (unitless constant)
## This part uses fix qtb to prepare alpha-quartz with quantum nuclear correction of the initial state
include alpha_quartz_qtb.mod
## This part demonstrates how to retart fix qbmsst during any stage of the shock simulation.
## PPPM may break down when compression ratio becomes extremely large. One can always use this restart technique to resume the shock simulation.
#Compression restart 1
reset_timestep 0
#Beta is the number of time steps between each update of the quantum bath temperature. Setting a larger beta can reduce thermal flactuations.
fix shock all qbmsst z ${v_msst} q ${q_msst} tscale ${tscale_msst} damp ${damp_qtb} f_max 120 N_f 100 seed 35082 eta ${eta_qbmsst} beta 5 T_init ${temperature}
fix_modify shock energy yes
variable dhug equal f_shock[1]
variable dray equal f_shock[2]
variable lgr_vel equal f_shock[3]
variable lgr_pos equal f_shock[4]
variable T_qm equal f_shock[5] #Temperature with quantum nuclear correction
thermo_style custom step v_T_qm press etotal vol lx ly lz pzz v_dhug v_dray v_lgr_vel v_lgr_pos
thermo 100
timestep ${delta_t}
run 1000
write_restart restart.1000
#Compression restart 2
#Read restart file and load potential again
clear
read_restart restart.1000
include alpha_quartz_potential.mod
#Use the same fix id and add no tscale if the system is already compressed
fix shock all qbmsst z ${v_msst} q ${q_msst} tscale 0.0 damp ${damp_qtb} f_max 120 N_f 100 seed 35082 eta ${eta_qbmsst} beta 5 T_init ${temperature}
fix_modify shock energy yes
variable dhug equal f_shock[1]
variable dray equal f_shock[2]
variable lgr_vel equal f_shock[3]
variable lgr_pos equal f_shock[4]
variable T_qm equal f_shock[5] #Temperature with quantum nuclear correction
thermo_style custom step v_T_qm press etotal vol lx ly lz pzz v_dhug v_dray v_lgr_vel v_lgr_pos
thermo 100
timestep ${delta_t}
restart 1000 restart
run 10000 #10 ps

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## This script first constructs an alpha quartz structure of a given size. It then uses fix qtb to equilibrate the computational cell to the specified temperature and pressure.
## This part defines units, alpha-quartz crystal, and atomic information
#General
units metal
dimension 3
boundary p p p
atom_style charge
#Lattice
lattice custom 1.0 &
a1 4.916000 0.000000 0.000000 &
a2 -2.45800 4.257381 0.000000 &
a3 0.000000 0.000000 5.405400 &
&
basis 0.469700 0.000000 0.000000 &
basis 0.000000 0.469700 0.666667 &
basis 0.530300 0.530300 0.333333 &
&
basis 0.413500 0.266900 0.119100 &
basis 0.266900 0.413500 0.547567 &
basis 0.733100 0.146600 0.785767 &
basis 0.586500 0.853400 0.214233 &
basis 0.853400 0.586500 0.452433 &
basis 0.146600 0.733100 0.880900 #American Mineralogist 65 920 1980 (Space Group 154)
#Computational Cell
region orthorhombic_unit_cell block 0 4.916000 0 8.514762 0 5.405400 units box
create_box 2 orthorhombic_unit_cell
create_atoms 1 box &
basis 1 1 &
basis 2 1 &
basis 3 1 &
basis 4 2 &
basis 5 2 &
basis 6 2 &
basis 7 2 &
basis 8 2 &
basis 9 2
replicate ${x_rep} ${y_rep} ${z_rep}
#Atomic Information
mass 1 28.085500
mass 2 15.999400
set type 1 charge +2.4
set type 2 charge -1.2
## This part implements the BKS pair potential with a cut-off distance for the Buckingham term. Long range Coulomb interactions are evaluated with the pppm method.
include alpha_quartz_potential.mod
## This part equilibrates your crystal to a pressure of ${pressure}(unit pressure) and a temperature of ${temperature}(unit temperatureture) with quantum nuclear effects
variable p_damp equal ${delta_t}*1000 #Recommended pressure damping parameter in fix nph
fix scapegoat_qtb all nph iso ${pressure} ${pressure} ${p_damp} #NPH does the time integration
fix quartz_qtb all qtb temp ${temperature} damp ${damp_qtb} seed 35082 f_max 120.00 N_f 100 #Change f_max (THz) if your Debye frequency is higher
thermo_style custom step temp press etotal vol lx ly lz pxx pyy pzz pxy pyz pxz
thermo 100
run 2000 # 2 ps
unfix quartz_qtb
unfix scapegoat_qtb

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## This script first constructs an alpha quartz structure of a given size. It then uses fix qtb to equilibrate the computational cell to the specified temperature and pressure.
variable x_rep equal 2 #x-direction replication number
variable y_rep equal 2 #y-direction replication number
variable z_rep equal 2 #z-direction replication number
variable cut_off equal 10.0 #Cut-off distance for the Buckingham term (Angstrom in metal units)
variable pressure equal 1.03125 #Initial state pressure (bar in metal units)
variable temperature equal 300.0 #Initial state quantum temperature (K in metal units)
variable delta_t equal 1.0e-3 #MD timestep length (ps in metal units)
variable damp_qtb equal 1 #1/gamma where gamma is the friction coefficient in quantum thermal bath (ps in metal units)
## This part defines units, alpha-quartz crystal, and atomic information
#General
units metal
dimension 3
boundary p p p
atom_style charge
#Lattice
lattice custom 1.0 &
a1 4.916000 0.000000 0.000000 &
a2 -2.45800 4.257381 0.000000 &
a3 0.000000 0.000000 5.405400 &
&
basis 0.469700 0.000000 0.000000 &
basis 0.000000 0.469700 0.666667 &
basis 0.530300 0.530300 0.333333 &
&
basis 0.413500 0.266900 0.119100 &
basis 0.266900 0.413500 0.547567 &
basis 0.733100 0.146600 0.785767 &
basis 0.586500 0.853400 0.214233 &
basis 0.853400 0.586500 0.452433 &
basis 0.146600 0.733100 0.880900 #American Mineralogist 65 920 1980 (Space Group 154)
#Computational Cell
region orthorhombic_unit_cell block 0 4.916000 0 8.514762 0 5.405400 units box
create_box 2 orthorhombic_unit_cell
create_atoms 1 box &
basis 1 1 &
basis 2 1 &
basis 3 1 &
basis 4 2 &
basis 5 2 &
basis 6 2 &
basis 7 2 &
basis 8 2 &
basis 9 2
replicate ${x_rep} ${y_rep} ${z_rep}
#Atomic Information
mass 1 28.085500
mass 2 15.999400
set type 1 charge +2.4
set type 2 charge -1.2
## This part implements the BKS pair potential with a cut-off distance for the Buckingham term. Long range Coulomb interactions are evaluated with the pppm method.
#Pair Potentials
pair_style buck/coul/long ${cut_off} #BKS interaction, PRL 64 1955 (1990)
pair_coeff 1 1 0.0 1.0 0.0
pair_coeff 1 2 18003.757200 0.205205 133.538100
pair_coeff 2 2 1388.773000 0.362319 175.000000
pair_modify shift yes
kspace_style pppm 1.0e-4
#Neighbor style
neighbor 2.0 bin
neigh_modify check yes every 1 delay 0 page 100000 one 2000
## This part equilibrates your crystal to a pressure of ${pressure}(unit pressure) and a temperature of ${temperature}(unit temperatureture) with quantum nuclear effects
variable p_damp equal ${delta_t}*1000 #Recommended pressure damping parameter in fix nph
fix scapegoat_qtb all nph iso ${pressure} ${pressure} ${p_damp} #NPH does the time integration
fix quartz_qtb all qtb temp ${temperature} damp ${damp_qtb} seed 35082 f_max 120.00 N_f 100 #Change f_max (THz) if your Debye frequency is higher
thermo_style custom step temp press etotal vol lx ly lz pxx pyy pzz pxy pyz pxz
thermo 100
run 20000 # 20 ps
unfix quartz_qtb
unfix scapegoat_qtb

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Reactive MD-force field
39 ! Number of general parameters
50.0000 !Overcoordination parameter
9.5469 !Overcoordination parameter
127.8302 !Valency angle conjugation parameter
3.0000 !Triple bond stabilisation parameter
6.5000 !Triple bond stabilisation parameter
0.0000 !C2-correction
1.0496 !Undercoordination parameter
9.0000 !Triple bond stabilisation parameter
11.5054 !Undercoordination parameter
13.4059 !Undercoordination parameter
0.0000 !Triple bond stabilization energy
0.0000 !Lower Taper-radius
10.0000 !Upper Taper-radius
2.8793 !Not used
33.8667 !Valency undercoordination
7.0994 !Valency angle/lone pair parameter
1.0563 !Valency angle
2.0384 !Valency angle parameter
6.1431 !Not used
6.9290 !Double bond/angle parameter
0.3989 !Double bond/angle parameter: overcoord
3.9954 !Double bond/angle parameter: overcoord
-2.4837 !Not used
5.7796 !Torsion/BO parameter
10.0000 !Torsion overcoordination
1.9487 !Torsion overcoordination
-1.2327 !Conjugation 0 (not used)
2.1645 !Conjugation
1.5591 !vdWaals shielding
0.1000 !Cutoff for bond order (*100)
2.0038 !Valency angle conjugation parameter
0.6121 !Overcoordination parameter
1.2172 !Overcoordination parameter
1.8512 !Valency/lone pair parameter
0.5000 !Not used
20.0000 !Not used
5.0000 !Molecular energy (not used)
0.0000 !Molecular energy (not used)
3.6942 !Valency angle conjugation parameter
5 ! Nr of atoms; cov.r; valency;a.m;Rvdw;Evdw;gammaEEM;cov.r2;#
alfa;gammavdW;valency;Eunder;Eover;chiEEM;etaEEM;n.u.
cov r3;Elp;Heat inc.;n.u.;n.u.;n.u.;n.u.
ov/un;val1;n.u.;val3,vval4
C 1.3763 4.0000 12.0000 1.8857 0.1818 0.8712 1.2596 4.0000
9.5928 2.0784 4.0000 22.6732 79.5548 5.7254 6.9235 0.0000
1.2065 0.0000 -0.8579 4.9417 28.3475 11.9957 0.8563 0.0000
-2.8846 4.1590 1.0564 4.0000 2.9663 0.0000 0.0000 0.0000
H 0.6646 1.0000 1.0080 1.6030 0.0600 0.7625 -0.1000 1.0000
9.3951 4.4187 1.0000 0.0000 121.1250 3.8196 9.8832 1.0000
-0.1000 0.0000 -0.1339 3.5803 2.8733 1.0000 1.0698 0.0000
-13.0615 3.0626 1.0338 1.0000 2.8793 0.0000 0.0000 0.0000
O 1.2699 2.0000 15.9990 1.9741 0.0880 1.0804 1.0624 6.0000
10.2186 7.7719 4.0000 27.3264 116.0768 8.5000 7.8386 2.0000
0.9446 8.6170 -1.2371 17.0845 3.7082 0.5350 0.9745 0.0000
-3.1456 2.6656 1.0493 4.0000 2.9225 0.0000 0.0000 0.0000
N 1.2226 3.0000 14.0000 1.9324 0.1376 0.8596 1.1839 5.0000
10.0667 7.8431 4.0000 32.5000 100.0000 6.8418 6.3404 2.0000
1.0497 14.5853 -1.1222 2.0637 3.2584 3.1136 0.9745 0.0000
-4.2059 2.6491 1.0183 4.0000 2.8793 0.0000 0.0000 0.0000
S 1.9405 2.0000 32.0600 2.0677 0.2099 1.0336 1.5479 6.0000
9.9575 4.9055 4.0000 52.9998 112.1416 6.5000 8.2545 2.0000
1.4601 9.7177 -2.3700 5.7487 23.2859 12.7147 0.9745 0.0000
-11.0000 2.7466 1.0338 4.0000 2.8793 0.0000 0.0000 0.0000
15 ! Nr of bonds; Edis1;LPpen;n.u.;pbe1;pbo5;13corr;pbo6
pbe2;pbo3;pbo4;n.u.;pbo1;pbo2;ovcorr
1 1 145.4070 103.0681 73.7841 0.2176 -0.7816 1.0000 28.4167 0.3217
0.1111 -0.1940 8.6733 1.0000 -0.0994 5.9724 1.0000 0.0000
1 2 167.1752 0.0000 0.0000 -0.4421 0.0000 1.0000 6.0000 0.5969
17.4194 1.0000 0.0000 1.0000 -0.0099 8.5445 0.0000 0.0000
2 2 188.1606 0.0000 0.0000 -0.3140 0.0000 1.0000 6.0000 0.6816
8.6247 1.0000 0.0000 1.0000 -0.0183 5.7082 0.0000 0.0000
1 3 171.0470 67.2480 130.3792 0.3600 -0.1696 1.0000 12.0338 0.3796
0.3647 -0.2660 7.4396 1.0000 -0.1661 5.0637 0.0000 0.0000
3 3 90.2465 160.9645 40.0000 0.9950 -0.2435 1.0000 28.1614 0.9704
0.8145 -0.1850 7.5281 1.0000 -0.1283 6.2396 1.0000 0.0000
1 4 134.9992 139.6314 78.5681 0.0420 -0.1370 1.0000 23.6247 0.2415
0.1522 -0.3161 7.0000 1.0000 -0.1301 5.4980 1.0000 0.0000
3 4 127.7074 177.1058 40.0000 0.4561 -0.1481 1.0000 31.4801 0.2000
0.8968 -0.3555 7.0000 1.0000 -0.1219 7.0000 1.0000 0.0000
4 4 151.9142 87.1928 151.4761 0.4280 -0.1001 1.0000 12.3631 0.6229
0.1721 -0.1614 12.1345 1.0000 -0.0882 5.3056 1.0000 0.0000
2 3 216.6018 0.0000 0.0000 -0.4201 0.0000 1.0000 6.0000 0.9143
4.7737 1.0000 0.0000 1.0000 -0.0591 5.9451 0.0000 0.0000
2 4 223.1853 0.0000 0.0000 -0.4661 0.0000 1.0000 6.0000 0.5178
7.8731 1.0000 0.0000 1.0000 -0.0306 6.1506 0.0000 0.0000
1 5 128.9942 74.5848 55.2528 0.1035 -0.5211 1.0000 18.9617 0.6000
0.2949 -0.2398 8.1175 1.0000 -0.1029 5.6731 1.0000 0.0000
2 5 151.5159 0.0000 0.0000 -0.4721 0.0000 1.0000 6.0000 0.6000
9.4366 1.0000 0.0000 1.0000 -0.0290 7.0050 1.0000 0.0000
3 5 0.0000 0.0000 0.0000 0.5563 -0.4038 1.0000 49.5611 0.6000
0.4259 -0.4577 12.7569 1.0000 -0.1100 7.1145 1.0000 0.0000
4 5 0.0000 0.0000 0.0000 0.4438 -0.2034 1.0000 40.3399 0.6000
0.3296 -0.3153 9.1227 1.0000 -0.1805 5.6864 1.0000 0.0000
5 5 96.1871 93.7006 68.6860 0.0955 -0.4781 1.0000 17.8574 0.6000
0.2723 -0.2373 9.7875 1.0000 -0.0950 6.4757 1.0000 0.0000
6 ! Nr of off-diagonal terms; Ediss;Ro;gamma;rsigma;rpi;rpi2
1 2 0.0455 1.7218 10.4236 1.0379 -1.0000 -1.0000
2 3 0.0469 1.9185 10.3707 0.9406 -1.0000 -1.0000
2 4 0.0999 1.8372 9.6539 0.9692 -1.0000 -1.0000
1 3 0.1186 1.9820 9.5927 1.2936 1.1203 1.0805
1 4 0.1486 1.8922 9.7989 1.3746 1.2091 1.1427
3 4 0.1051 2.0060 10.0691 1.3307 1.1034 1.0060
50 ! Nr of angles;at1;at2;at3;Thetao,o;ka;kb;pv1;pv2
1 1 1 70.0265 13.6338 2.1884 0.0000 0.1676 26.3587 1.0400
1 1 2 69.7786 10.3544 8.4326 0.0000 0.1153 0.0000 1.0400
2 1 2 74.6020 11.8629 2.9294 0.0000 0.1367 0.0000 1.0400
1 2 2 0.0000 0.0000 6.0000 0.0000 0.0000 0.0000 1.0400
1 2 1 0.0000 3.4110 7.7350 0.0000 0.0000 0.0000 1.0400
2 2 2 0.0000 27.9213 5.8635 0.0000 0.0000 0.0000 1.0400
1 1 3 72.9588 16.7105 3.5244 0.0000 1.1127 0.0000 1.1880
3 1 3 80.0708 45.0000 2.1487 0.0000 1.1127 -35.0000 1.1880
1 1 4 61.5055 45.0000 1.2242 0.0000 1.1127 0.0000 1.1880
3 1 4 71.9345 45.0000 1.5052 0.0000 1.1127 0.0000 1.1880
4 1 4 51.3604 45.0000 0.6846 0.0000 1.1127 0.0000 1.1880
2 1 3 66.6150 13.6403 3.8212 0.0000 0.0755 0.0000 1.0500
2 1 4 68.9632 16.3575 3.1449 0.0000 0.0755 0.0000 1.0500
1 2 4 0.0000 0.0019 6.3000 0.0000 0.0000 0.0000 1.0400
1 3 1 79.1091 45.0000 0.7067 0.0000 0.6142 0.0000 1.0783
1 3 3 83.7151 42.6867 0.9699 0.0000 0.6142 0.0000 1.0783
1 3 4 79.5876 45.0000 1.1761 0.0000 0.6142 0.0000 1.0783
3 3 3 80.0108 38.3716 1.1572 -38.4200 0.6142 0.0000 1.0783
3 3 4 81.5614 19.8012 3.9968 0.0000 0.6142 0.0000 1.0783
4 3 4 85.3564 36.5858 1.7504 0.0000 0.6142 0.0000 1.0783
1 3 2 78.1533 44.7226 1.3136 0.0000 0.1218 0.0000 1.0500
2 3 3 84.1057 9.6413 7.5000 0.0000 0.1218 0.0000 1.0500
2 3 4 79.4629 44.0409 2.2959 0.0000 0.1218 0.0000 1.0500
2 3 2 79.2954 26.3838 2.2044 0.0000 0.1218 0.0000 1.0500
1 4 1 66.1477 22.9891 1.5923 0.0000 1.6777 0.0000 1.0500
1 4 3 91.9273 38.0207 0.5387 0.0000 1.6777 0.0000 1.0500
1 4 4 92.6933 9.9708 1.6094 0.0000 1.6777 0.0000 1.0500
3 4 3 73.4749 42.7640 1.7325 -17.5007 1.6777 0.0000 1.0500
3 4 4 73.9183 44.8857 1.1980 -0.9193 1.6777 0.0000 1.0500
4 4 4 74.0572 15.4709 5.4220 0.0000 1.6777 0.0000 1.0500
1 4 2 72.7016 33.4153 1.0224 0.0000 0.0222 0.0000 1.0500
2 4 3 82.4368 44.1900 1.9273 0.0000 0.0222 0.0000 1.0500
2 4 4 82.6883 39.9831 1.1916 0.0000 0.0222 0.0000 1.0500
2 4 2 71.2183 14.4528 3.6870 0.0000 0.0222 0.0000 1.0500
1 2 3 0.0000 0.0019 6.0000 0.0000 0.0000 0.0000 1.0400
1 2 4 0.0000 0.0019 6.0000 0.0000 0.0000 0.0000 1.0400
1 2 5 0.0000 0.0019 6.0000 0.0000 0.0000 0.0000 1.0400
3 2 3 0.0000 0.0019 6.0000 0.0000 0.0000 0.0000 1.0400
3 2 4 0.0000 0.0019 6.0000 0.0000 0.0000 0.0000 1.0400
4 2 4 0.0000 0.0019 6.0000 0.0000 0.0000 0.0000 1.0400
2 2 3 0.0000 0.0019 6.0000 0.0000 0.0000 0.0000 1.0400
2 2 4 0.0000 0.0019 6.0000 0.0000 0.0000 0.0000 1.0400
1 1 5 74.9397 25.0560 1.8787 0.1463 0.0559 0.0000 1.0400
1 5 1 86.9521 36.9951 2.0903 0.1463 0.0559 0.0000 1.0400
2 1 5 74.9397 25.0560 1.8787 0.0000 0.0000 0.0000 1.0400
1 5 2 86.1791 36.9951 2.0903 0.0000 0.0000 0.0000 1.0400
1 5 5 85.3644 36.9951 2.0903 0.1463 0.0559 0.0000 1.0400
2 5 2 93.1959 36.9951 2.0903 0.0000 0.0000 0.0000 1.0400
2 5 5 84.3331 36.9951 2.0903 0.0000 0.0000 0.0000 1.0400
2 2 5 0.0000 0.0019 6.0000 0.0000 0.0000 0.0000 1.0400
17 ! Nr of torsions;at1;at2;at3;at4;;V1;V2;V3;V2(BO);vconj;n.u;n
1 1 1 1 0.0000 23.2168 0.1811 -4.6220 -1.9387 0.0000 0.0000
1 1 1 2 0.0000 45.7984 0.3590 -5.7106 -2.9459 0.0000 0.0000
2 1 1 2 0.0000 44.6445 0.3486 -5.1725 -0.8717 0.0000 0.0000
0 1 2 0 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000
0 2 2 0 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000
0 1 3 0 5.0520 16.7344 0.5590 -3.0181 -2.0000 0.0000 0.0000
0 2 3 0 0.0000 0.1000 0.0200 -2.5415 0.0000 0.0000 0.0000
0 3 3 0 0.0115 68.9706 0.8253 -28.4693 0.0000 0.0000 0.0000
0 1 4 0 -4.0616 66.2036 0.3855 -4.4414 -2.0000 0.0000 0.0000
0 2 4 0 0.0000 0.1000 0.0200 -2.5415 0.0000 0.0000 0.0000
0 3 4 0 1.1130 14.8049 0.0231 -10.7175 -2.0000 0.0000 0.0000
0 4 4 0 -0.0851 37.4200 0.0107 -3.5209 -2.0000 0.0000 0.0000
0 1 1 0 0.0000 0.9305 0.0000 -24.2568 0.0000 0.0000 0.0000
4 1 4 4 -3.6064 43.6430 0.0004 -11.5507 -2.0000 0.0000 0.0000
0 1 5 0 3.3423 30.3435 0.0365 -2.7171 0.0000 0.0000 0.0000
0 5 5 0 -0.0555 -42.7738 0.1515 -2.2056 0.0000 0.0000 0.0000
0 2 5 0 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000
9 ! Nr of hydrogen bonds;at1;at2;at3;Rhb;Dehb;vhb1
3 2 3 2.0431 -6.6813 3.5000 1.7295
3 2 4 1.6740 -10.9581 3.5000 1.7295
4 2 3 1.4889 -9.6465 3.5000 1.7295
4 2 4 1.8324 -8.0074 3.5000 1.7295
3 2 5 2.6644 -3.9547 3.5000 1.7295
4 2 5 4.0476 -5.7038 3.5000 1.7295
5 2 3 2.1126 -4.5790 3.5000 1.7295
5 2 4 2.2066 -5.7038 3.5000 1.7295
5 2 5 1.9461 -4.0000 3.5000 1.7295

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## This script first uses fix qtb to equilibrate liquid methane to an initial state with quantum nuclear correction and then simulate shock induced chemical reactions through the quantum thermal bath multi-scale shock technique
#The default system size may take a while to run you can change to a smaller size
variable x_rep equal 5 #x-direction replication number
variable y_rep equal 5 #y-direction replication number
variable z_rep equal 10 #z-direction replication number
variable temperature equal 110.0 #Target quantum temperature (K in real units)
variable delta_t equal 0.25 #MD timestep length (fs in real units)
variable damp_qtb equal 200 #1/gamma where gamma is the friction coefficient in quantum thermal bath (fs in real units)
variable v_msst equal 0.122 #Shock velocity (Angstrom/fs in metal units)
variable q_msst equal 25.0 #Box mass-like parameter in the MSST (mass^2/length^4, where mass=grams/mole and length=Angstrom in real units)
variable mu_msst equal 0.9 #Artificial viscosity in the MSST (mass/length/time, where mass=grams/mole, length=Angstrom and time=fs in real units)
variable tscale_msst equal 0.01 #Temperature reduction parameter in the MSST (unitless)
variable eta_qbmsst equal 1.0 #Coupling constant between the shock and the quantum thermal bath (unitless constant)
##The included part first constructs a liquid methane structure of a given size. It then uses fix qtb to equilibrate the computational cell to the specified temperature and pressure.
include methane_qtb.mod
##Shock compression with quantum nuclear corrections
reset_timestep 0
fix shock all qbmsst z ${v_msst} q ${q_msst} mu ${mu_msst} tscale ${tscale_msst} damp ${damp_qtb} f_max 0.3 N_f 50 seed 35082 eta ${eta_qbmsst} beta 400 T_init ${temperature}
fix_modify shock energy yes
variable dhug equal f_shock[1]
variable dray equal f_shock[2]
variable lgr_vel equal f_shock[3]
variable lgr_pos equal f_shock[4]
variable T_qm equal f_shock[5] #Temperature with quantum nuclear correction
thermo_style custom step v_T_qm press etotal vol lx ly lz pzz v_dhug v_dray v_lgr_vel v_lgr_pos
thermo 100
timestep ${delta_t}
restart 1000 restart
run 5000

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## This script first constructs a liquid methane structure of a given size. It then uses fix qtb to equilibrate the computational cell to the specified temperature and pressure.
## This part defines units, methane structure, and atomic information
#General
units real
dimension 3
boundary p p p
atom_style charge
#Lattice
lattice custom 1.0 &
a1 3.9783624 0 0 &
a2 0 3.9783624 0 &
a3 0 0 3.9783624 &
&
basis 0.5 0.5 0.5 &
basis 0.663 0.663 0.663 &
basis 0.337 0.337 0.663 &
basis 0.663 0.337 0.337 &
basis 0.337 0.663 0.337
#Computational Cell
region simbox block 0 3.9783624 0 3.9783624 0 3.9783624 units box
create_box 2 simbox
create_atoms 1 box &
basis 1 1 &
basis 2 2 &
basis 3 2 &
basis 4 2 &
basis 5 2
replicate ${x_rep} ${y_rep} ${z_rep}
#Atomic Information
mass 1 12.011150
mass 2 1.007970
## This part defines the reax pair potential in methane, force field coefficients are specified in "ffield.reax"
#Pair Potentials
pair_style reax 10.0 1 1 1.0e-6
pair_coeff * * ffield.reax 1 2
#Neighbor Style
neighbor 2.5 bin
neigh_modify every 10 delay 0 check no
## This part equilibrates liquid methane to a temperature of ${temperature}(unit temperatureture) with quantum nuclear effects
#Initilization
velocity all create ${temperature} 93 dist gaussian sum no mom yes rot yes loop all
#Setup output
thermo_style custom step temp press etotal vol
thermo 100
#Colored thermal bath
fix scapegoat_qtb all nve #NVE does the time integration
fix methane_qtb all qtb temp ${temperature} damp ${damp_qtb} seed 35082 f_max 0.3 N_f 50 #Change f_max if your Debye frequency is higher
timestep ${delta_t}
run 2000 #500 fs
unfix methane_qtb
unfix scapegoat_qtb

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Reactive MD-force field
39 ! Number of general parameters
50.0000 !Overcoordination parameter
9.5469 !Overcoordination parameter
127.8302 !Valency angle conjugation parameter
3.0000 !Triple bond stabilisation parameter
6.5000 !Triple bond stabilisation parameter
0.0000 !C2-correction
1.0496 !Undercoordination parameter
9.0000 !Triple bond stabilisation parameter
11.5054 !Undercoordination parameter
13.4059 !Undercoordination parameter
0.0000 !Triple bond stabilization energy
0.0000 !Lower Taper-radius
10.0000 !Upper Taper-radius
2.8793 !Not used
33.8667 !Valency undercoordination
7.0994 !Valency angle/lone pair parameter
1.0563 !Valency angle
2.0384 !Valency angle parameter
6.1431 !Not used
6.9290 !Double bond/angle parameter
0.3989 !Double bond/angle parameter: overcoord
3.9954 !Double bond/angle parameter: overcoord
-2.4837 !Not used
5.7796 !Torsion/BO parameter
10.0000 !Torsion overcoordination
1.9487 !Torsion overcoordination
-1.2327 !Conjugation 0 (not used)
2.1645 !Conjugation
1.5591 !vdWaals shielding
0.1000 !Cutoff for bond order (*100)
2.0038 !Valency angle conjugation parameter
0.6121 !Overcoordination parameter
1.2172 !Overcoordination parameter
1.8512 !Valency/lone pair parameter
0.5000 !Not used
20.0000 !Not used
5.0000 !Molecular energy (not used)
0.0000 !Molecular energy (not used)
3.6942 !Valency angle conjugation parameter
5 ! Nr of atoms; cov.r; valency;a.m;Rvdw;Evdw;gammaEEM;cov.r2;#
alfa;gammavdW;valency;Eunder;Eover;chiEEM;etaEEM;n.u.
cov r3;Elp;Heat inc.;n.u.;n.u.;n.u.;n.u.
ov/un;val1;n.u.;val3,vval4
C 1.3763 4.0000 12.0000 1.8857 0.1818 0.8712 1.2596 4.0000
9.5928 2.0784 4.0000 22.6732 79.5548 5.7254 6.9235 0.0000
1.2065 0.0000 -0.8579 4.9417 28.3475 11.9957 0.8563 0.0000
-2.8846 4.1590 1.0564 4.0000 2.9663 0.0000 0.0000 0.0000
H 0.6646 1.0000 1.0080 1.6030 0.0600 0.7625 -0.1000 1.0000
9.3951 4.4187 1.0000 0.0000 121.1250 3.8196 9.8832 1.0000
-0.1000 0.0000 -0.1339 3.5803 2.8733 1.0000 1.0698 0.0000
-13.0615 3.0626 1.0338 1.0000 2.8793 0.0000 0.0000 0.0000
O 1.2699 2.0000 15.9990 1.9741 0.0880 1.0804 1.0624 6.0000
10.2186 7.7719 4.0000 27.3264 116.0768 8.5000 7.8386 2.0000
0.9446 8.6170 -1.2371 17.0845 3.7082 0.5350 0.9745 0.0000
-3.1456 2.6656 1.0493 4.0000 2.9225 0.0000 0.0000 0.0000
N 1.2226 3.0000 14.0000 1.9324 0.1376 0.8596 1.1839 5.0000
10.0667 7.8431 4.0000 32.5000 100.0000 6.8418 6.3404 2.0000
1.0497 14.5853 -1.1222 2.0637 3.2584 3.1136 0.9745 0.0000
-4.2059 2.6491 1.0183 4.0000 2.8793 0.0000 0.0000 0.0000
S 1.9405 2.0000 32.0600 2.0677 0.2099 1.0336 1.5479 6.0000
9.9575 4.9055 4.0000 52.9998 112.1416 6.5000 8.2545 2.0000
1.4601 9.7177 -2.3700 5.7487 23.2859 12.7147 0.9745 0.0000
-11.0000 2.7466 1.0338 4.0000 2.8793 0.0000 0.0000 0.0000
15 ! Nr of bonds; Edis1;LPpen;n.u.;pbe1;pbo5;13corr;pbo6
pbe2;pbo3;pbo4;n.u.;pbo1;pbo2;ovcorr
1 1 145.4070 103.0681 73.7841 0.2176 -0.7816 1.0000 28.4167 0.3217
0.1111 -0.1940 8.6733 1.0000 -0.0994 5.9724 1.0000 0.0000
1 2 167.1752 0.0000 0.0000 -0.4421 0.0000 1.0000 6.0000 0.5969
17.4194 1.0000 0.0000 1.0000 -0.0099 8.5445 0.0000 0.0000
2 2 188.1606 0.0000 0.0000 -0.3140 0.0000 1.0000 6.0000 0.6816
8.6247 1.0000 0.0000 1.0000 -0.0183 5.7082 0.0000 0.0000
1 3 171.0470 67.2480 130.3792 0.3600 -0.1696 1.0000 12.0338 0.3796
0.3647 -0.2660 7.4396 1.0000 -0.1661 5.0637 0.0000 0.0000
3 3 90.2465 160.9645 40.0000 0.9950 -0.2435 1.0000 28.1614 0.9704
0.8145 -0.1850 7.5281 1.0000 -0.1283 6.2396 1.0000 0.0000
1 4 134.9992 139.6314 78.5681 0.0420 -0.1370 1.0000 23.6247 0.2415
0.1522 -0.3161 7.0000 1.0000 -0.1301 5.4980 1.0000 0.0000
3 4 127.7074 177.1058 40.0000 0.4561 -0.1481 1.0000 31.4801 0.2000
0.8968 -0.3555 7.0000 1.0000 -0.1219 7.0000 1.0000 0.0000
4 4 151.9142 87.1928 151.4761 0.4280 -0.1001 1.0000 12.3631 0.6229
0.1721 -0.1614 12.1345 1.0000 -0.0882 5.3056 1.0000 0.0000
2 3 216.6018 0.0000 0.0000 -0.4201 0.0000 1.0000 6.0000 0.9143
4.7737 1.0000 0.0000 1.0000 -0.0591 5.9451 0.0000 0.0000
2 4 223.1853 0.0000 0.0000 -0.4661 0.0000 1.0000 6.0000 0.5178
7.8731 1.0000 0.0000 1.0000 -0.0306 6.1506 0.0000 0.0000
1 5 128.9942 74.5848 55.2528 0.1035 -0.5211 1.0000 18.9617 0.6000
0.2949 -0.2398 8.1175 1.0000 -0.1029 5.6731 1.0000 0.0000
2 5 151.5159 0.0000 0.0000 -0.4721 0.0000 1.0000 6.0000 0.6000
9.4366 1.0000 0.0000 1.0000 -0.0290 7.0050 1.0000 0.0000
3 5 0.0000 0.0000 0.0000 0.5563 -0.4038 1.0000 49.5611 0.6000
0.4259 -0.4577 12.7569 1.0000 -0.1100 7.1145 1.0000 0.0000
4 5 0.0000 0.0000 0.0000 0.4438 -0.2034 1.0000 40.3399 0.6000
0.3296 -0.3153 9.1227 1.0000 -0.1805 5.6864 1.0000 0.0000
5 5 96.1871 93.7006 68.6860 0.0955 -0.4781 1.0000 17.8574 0.6000
0.2723 -0.2373 9.7875 1.0000 -0.0950 6.4757 1.0000 0.0000
6 ! Nr of off-diagonal terms; Ediss;Ro;gamma;rsigma;rpi;rpi2
1 2 0.0455 1.7218 10.4236 1.0379 -1.0000 -1.0000
2 3 0.0469 1.9185 10.3707 0.9406 -1.0000 -1.0000
2 4 0.0999 1.8372 9.6539 0.9692 -1.0000 -1.0000
1 3 0.1186 1.9820 9.5927 1.2936 1.1203 1.0805
1 4 0.1486 1.8922 9.7989 1.3746 1.2091 1.1427
3 4 0.1051 2.0060 10.0691 1.3307 1.1034 1.0060
50 ! Nr of angles;at1;at2;at3;Thetao,o;ka;kb;pv1;pv2
1 1 1 70.0265 13.6338 2.1884 0.0000 0.1676 26.3587 1.0400
1 1 2 69.7786 10.3544 8.4326 0.0000 0.1153 0.0000 1.0400
2 1 2 74.6020 11.8629 2.9294 0.0000 0.1367 0.0000 1.0400
1 2 2 0.0000 0.0000 6.0000 0.0000 0.0000 0.0000 1.0400
1 2 1 0.0000 3.4110 7.7350 0.0000 0.0000 0.0000 1.0400
2 2 2 0.0000 27.9213 5.8635 0.0000 0.0000 0.0000 1.0400
1 1 3 72.9588 16.7105 3.5244 0.0000 1.1127 0.0000 1.1880
3 1 3 80.0708 45.0000 2.1487 0.0000 1.1127 -35.0000 1.1880
1 1 4 61.5055 45.0000 1.2242 0.0000 1.1127 0.0000 1.1880
3 1 4 71.9345 45.0000 1.5052 0.0000 1.1127 0.0000 1.1880
4 1 4 51.3604 45.0000 0.6846 0.0000 1.1127 0.0000 1.1880
2 1 3 66.6150 13.6403 3.8212 0.0000 0.0755 0.0000 1.0500
2 1 4 68.9632 16.3575 3.1449 0.0000 0.0755 0.0000 1.0500
1 2 4 0.0000 0.0019 6.3000 0.0000 0.0000 0.0000 1.0400
1 3 1 79.1091 45.0000 0.7067 0.0000 0.6142 0.0000 1.0783
1 3 3 83.7151 42.6867 0.9699 0.0000 0.6142 0.0000 1.0783
1 3 4 79.5876 45.0000 1.1761 0.0000 0.6142 0.0000 1.0783
3 3 3 80.0108 38.3716 1.1572 -38.4200 0.6142 0.0000 1.0783
3 3 4 81.5614 19.8012 3.9968 0.0000 0.6142 0.0000 1.0783
4 3 4 85.3564 36.5858 1.7504 0.0000 0.6142 0.0000 1.0783
1 3 2 78.1533 44.7226 1.3136 0.0000 0.1218 0.0000 1.0500
2 3 3 84.1057 9.6413 7.5000 0.0000 0.1218 0.0000 1.0500
2 3 4 79.4629 44.0409 2.2959 0.0000 0.1218 0.0000 1.0500
2 3 2 79.2954 26.3838 2.2044 0.0000 0.1218 0.0000 1.0500
1 4 1 66.1477 22.9891 1.5923 0.0000 1.6777 0.0000 1.0500
1 4 3 91.9273 38.0207 0.5387 0.0000 1.6777 0.0000 1.0500
1 4 4 92.6933 9.9708 1.6094 0.0000 1.6777 0.0000 1.0500
3 4 3 73.4749 42.7640 1.7325 -17.5007 1.6777 0.0000 1.0500
3 4 4 73.9183 44.8857 1.1980 -0.9193 1.6777 0.0000 1.0500
4 4 4 74.0572 15.4709 5.4220 0.0000 1.6777 0.0000 1.0500
1 4 2 72.7016 33.4153 1.0224 0.0000 0.0222 0.0000 1.0500
2 4 3 82.4368 44.1900 1.9273 0.0000 0.0222 0.0000 1.0500
2 4 4 82.6883 39.9831 1.1916 0.0000 0.0222 0.0000 1.0500
2 4 2 71.2183 14.4528 3.6870 0.0000 0.0222 0.0000 1.0500
1 2 3 0.0000 0.0019 6.0000 0.0000 0.0000 0.0000 1.0400
1 2 4 0.0000 0.0019 6.0000 0.0000 0.0000 0.0000 1.0400
1 2 5 0.0000 0.0019 6.0000 0.0000 0.0000 0.0000 1.0400
3 2 3 0.0000 0.0019 6.0000 0.0000 0.0000 0.0000 1.0400
3 2 4 0.0000 0.0019 6.0000 0.0000 0.0000 0.0000 1.0400
4 2 4 0.0000 0.0019 6.0000 0.0000 0.0000 0.0000 1.0400
2 2 3 0.0000 0.0019 6.0000 0.0000 0.0000 0.0000 1.0400
2 2 4 0.0000 0.0019 6.0000 0.0000 0.0000 0.0000 1.0400
1 1 5 74.9397 25.0560 1.8787 0.1463 0.0559 0.0000 1.0400
1 5 1 86.9521 36.9951 2.0903 0.1463 0.0559 0.0000 1.0400
2 1 5 74.9397 25.0560 1.8787 0.0000 0.0000 0.0000 1.0400
1 5 2 86.1791 36.9951 2.0903 0.0000 0.0000 0.0000 1.0400
1 5 5 85.3644 36.9951 2.0903 0.1463 0.0559 0.0000 1.0400
2 5 2 93.1959 36.9951 2.0903 0.0000 0.0000 0.0000 1.0400
2 5 5 84.3331 36.9951 2.0903 0.0000 0.0000 0.0000 1.0400
2 2 5 0.0000 0.0019 6.0000 0.0000 0.0000 0.0000 1.0400
17 ! Nr of torsions;at1;at2;at3;at4;;V1;V2;V3;V2(BO);vconj;n.u;n
1 1 1 1 0.0000 23.2168 0.1811 -4.6220 -1.9387 0.0000 0.0000
1 1 1 2 0.0000 45.7984 0.3590 -5.7106 -2.9459 0.0000 0.0000
2 1 1 2 0.0000 44.6445 0.3486 -5.1725 -0.8717 0.0000 0.0000
0 1 2 0 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000
0 2 2 0 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000
0 1 3 0 5.0520 16.7344 0.5590 -3.0181 -2.0000 0.0000 0.0000
0 2 3 0 0.0000 0.1000 0.0200 -2.5415 0.0000 0.0000 0.0000
0 3 3 0 0.0115 68.9706 0.8253 -28.4693 0.0000 0.0000 0.0000
0 1 4 0 -4.0616 66.2036 0.3855 -4.4414 -2.0000 0.0000 0.0000
0 2 4 0 0.0000 0.1000 0.0200 -2.5415 0.0000 0.0000 0.0000
0 3 4 0 1.1130 14.8049 0.0231 -10.7175 -2.0000 0.0000 0.0000
0 4 4 0 -0.0851 37.4200 0.0107 -3.5209 -2.0000 0.0000 0.0000
0 1 1 0 0.0000 0.9305 0.0000 -24.2568 0.0000 0.0000 0.0000
4 1 4 4 -3.6064 43.6430 0.0004 -11.5507 -2.0000 0.0000 0.0000
0 1 5 0 3.3423 30.3435 0.0365 -2.7171 0.0000 0.0000 0.0000
0 5 5 0 -0.0555 -42.7738 0.1515 -2.2056 0.0000 0.0000 0.0000
0 2 5 0 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000
9 ! Nr of hydrogen bonds;at1;at2;at3;Rhb;Dehb;vhb1
3 2 3 2.0431 -6.6813 3.5000 1.7295
3 2 4 1.6740 -10.9581 3.5000 1.7295
4 2 3 1.4889 -9.6465 3.5000 1.7295
4 2 4 1.8324 -8.0074 3.5000 1.7295
3 2 5 2.6644 -3.9547 3.5000 1.7295
4 2 5 4.0476 -5.7038 3.5000 1.7295
5 2 3 2.1126 -4.5790 3.5000 1.7295
5 2 4 2.2066 -5.7038 3.5000 1.7295
5 2 5 1.9461 -4.0000 3.5000 1.7295

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## This script first constructs a liquid methane structure of a given size. It then uses fix qtb to equilibrate the computational cell to the specified temperature and pressure.
variable x_rep equal 2 #x-direction replication number
variable y_rep equal 2 #y-direction replication number
variable z_rep equal 2 #z-direction replication number
variable temperature equal 110.0 #Target quantum temperature (K in real units)
variable delta_t equal 0.25 #MD timestep length (fs in real units)
variable damp_qtb equal 200 #1/gamma where gamma is the friction coefficient in quantum thermal bath (fs in real units)
## This part defines units, methane structure, and atomic information
#General
units real
dimension 3
boundary p p p
atom_style charge
#Lattice
lattice custom 1.0 &
a1 3.9783624 0 0 &
a2 0 3.9783624 0 &
a3 0 0 3.9783624 &
&
basis 0.5 0.5 0.5 &
basis 0.663 0.663 0.663 &
basis 0.337 0.337 0.663 &
basis 0.663 0.337 0.337 &
basis 0.337 0.663 0.337
#Computational Cell
region simbox block 0 3.9783624 0 3.9783624 0 3.9783624 units box
create_box 2 simbox
create_atoms 1 box &
basis 1 1 &
basis 2 2 &
basis 3 2 &
basis 4 2 &
basis 5 2
replicate ${x_rep} ${y_rep} ${z_rep}
#Atomic Information
mass 1 12.011150
mass 2 1.007970
## This part defines the reax pair potential in methane, force field coefficients are specified in "ffield.reax"
#Pair Potentials
pair_style reax 10.0 1 1 1.0e-6
pair_coeff * * ffield.reax 1 2
#Neighbor Style
neighbor 2.5 bin
neigh_modify every 10 delay 0 check no
## This part equilibrates liquid methane to a temperature of ${temperature}(unit temperatureture) with quantum nuclear effects
#Initilization
velocity all create ${temperature} 93 dist gaussian sum no mom yes rot yes loop all
#Setup output
thermo_style custom step temp press etotal vol
thermo 100
#Colored thermal bath
fix scapegoat_qtb all nve #NVE does the time integration
fix methane_qtb all qtb temp ${temperature} damp ${damp_qtb} seed 35082 f_max 0.3 N_f 50 #Change f_max if your Debye frequency is higher
timestep ${delta_t}
run 3000 #750 fs
unfix methane_qtb
unfix scapegoat_qtb